1. Field of the Invention
This invention relates to helicopter cross-beam rotors and more particular to such rotors which have a replaceable primary snubber between the flexible spar and the enveloping torque tube, and more particularly to such rotors in which the primary snubber is connected to the spar in slip-fit engagement with the retainer member which is bonded to the spar with an elastomer layer of selected shape factor so as to cause the retainer to remain bonded to the spar throughout all motions of the flexible spar, and which primary snubber is used in combination with an auxiliary snubber.
2. Description of the Prior Art
In the prior art, such snubbers have been bonded directly to the flexible spar. This has proved to be undesirable because replacement thereof in the field can actually cause damage to the spar per se, which is the main load carrying element in the helicopter rotor, thereby threatening structural integrity of the rotor. Snubbers have also been used in the prior art between the blade and the hub, such as in U.S. Pat. No. 4,053,258 to Mouille entitled "Tail-Rotor Arrangement for Rotor Crafts," and the disadvantage of this blade-to-hub snubber, as opposed to our blade-to-spar snubber, is that the blade-to-hub snubber causes higher cyclic flapwise bending stresses to occur in the torque tube member as the spar flexes in flight, whereas, the blade-to-spar snubber is mounted outboard of the point of maximum spar bending curvature thereby reducing torque tube deflections and stresses. Further, our laminated metal shim/elastomer snubber has the following advantages over the solid rubber snubber of Mouille: (1) higher compression strength and improved fatigue life since bulging of the elastomer at the free edges is greatly reduced in the laminated construction because the thin rubber layers permitted by the laminated construction have a high shape factor, and (2) higher compression stiffness due to the higher shape factor attainable with the laminated construction. This higher stiffness aids rotor stability and reduces lost control motion due to snubber deflections caused the pitch control loads.